C++ :: Passing Data Between Threads Without Using Global Variables
Nov 6, 2013I have a main thread and a worker thread. How do i pass data between them when both are already running without using global variables?
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C :: Use Pointers Instead Of Global Variables?
Oct 15, 2014I have made an application and I have basically solved everything. But the only problem is that I am using global variables because it felt like the smoothest, so my program is built on it.
But now I've read around and I understand that you should not use these(?). Do you think pointers is the best think to use instead?I have previously declared my board array and some variables as global and I want them in alot of functions.I have read and understand the procedure for the use of pointers so I can use my int's in the other functions by doing like this? Code: #include <stdio.h>
int justprint();
int main()
{
int Row = 2;
int Column = 2;
int *pRow = &Row;
int *pColumn = &Column;
[code]...
But how do I do it with an array like this one? If I declare it in the main function, and then want to use it in other functions.Or are there better, easier solutions?
Code: char game[3][3]={{0,0}};
C++ :: Access EXE Global Variables From DLL
Jun 25, 2013On linux, I can compile DLLs (shared objects) as well as executables that use them. I can even access globals and classes that are defined in the EXE from the DLL, and vice versa, simply with the 'export' keyword. flawlessly.
The Problem: But on Windows (using MinGW), no matter what I do, I'm completely unable to access global variables which defined in the EXE, from the DLL. On Linux, this is no sweat, but what's Windows' problem?
I also need to extend classes in the dll with base class method definitions defined in the exe.
Ive heard that on Windows, you need to use declspec(dllimport) and declspec(dllexport). I can compile with CygWin+MinGW/g++4.5.3 as well as "Pure Windows" with MinGW/g++4.7.2 *without* the declspecs. So what's the decljunk for? Is this really just something for MSVC or other compilers?
Here's some Windows code to show what the problem is. The DLL's global variable is accessible to the EXE just fine, but the EXE's global variable is not accessible to the DLL - compilation complains it is an undefined reference.
main.cpp
#include "myLib.h"
#include <stdio.h>
int exe;
[Code].....
edit: I tried using --enable-runtime-pseudo-reloc --allow-shlib-undefined options when compiling the DLL and G++ complains that --allow-shlib-undefined is an unrecognized option.
C++ :: Setup Global Variables
Feb 23, 2015I am using VS2010 to develop an app which includes several windows forms that I am trying to set up global variables for, and I am getting a few errors like:
LNK2005: "wchar_t *dsn"...already defined in ....obj
I have a header file (externals.h) with:
#ifndef MY_GLOBALS_H
#define MY_GLOBALS_H
extern long dbg;
extern wchar_t dsn[50];
extern wchar_t u[30];
extern wchar_t p[30];
#endif
and 2 different forms, each with different namespaces, but both including the above header (#include "externals.h").One of the form .h files defines the values for these externally declared variables like this: namespace PWValidationTools{
wchar_t dsn[50] =_T("MDOTProjectWise");
wchar_t u[30]=_T("api_admin");
wchar_t p[30]=_T("proce55");
long dbg = 1;
public ref class ValidationSetupForm : public System::Windows::Forms::Form {
}
The other form file only uses these variables, never defines them.I am getting the above LNK2005 error only for the variables declared as wchar_t, not the "long" one. why I'm getting the link errors only for the wchar_t variables.
C++ :: Global Variables For Multiple CPP Files
Jan 19, 2014I am trying to get variables that are global to multiple files. I have mananged to make constant variables that are global but maybe not in the best way. In the header i have the constant variables being defined:
const int variable_Name = 5;
And the cpp file:
#include <iostream>
using namespace std;
#include "vars.h"
int main ( ) {
cout << variable_Name<< endl;
system ("pause");
return 0;
}
Is there a better way to do this and to make the variables able to be changed within the cpp files.
C++ :: Using Global Variables In Static Library
Jul 22, 2014Is it possible to use & change global variables in a Static Library? For example:
I declare a
bool test = true;
globally.
Then later in an exported function If the user wants, he can set that test to false. So the program later when checks test if it's true, will notice that it's not true, since one of my function changed it.
Is it right?
C/C++ :: Passing A Global Pointer?
Feb 29, 2012Let's say I've got something like this:
struct Box{
//something
};
typedef struct Box* pBox;
[Code]....
function fun recieves the address(which is NULL) and then allocates the memory for the Box; Let's say I cannot return the address of new allocated p and I can't also use that pointer p(from main) without passing it into a function.
Q: How can I make it that I could operate in function "fun" as I operate on orginal pointer p(from main), right now I'm just passing the address to my function but I can't change the 'global' pointer p ;(.
I remember in pascal it's like:
"function(var pointer:[pointer to sth])"
and all is done.
C/C++ :: Why Implicit Int Approach Taken With No Specifier Only For Global Variables
Sep 22, 2013I realize that implicit int rule was removed in C99 but gcc still takes this approach by default. I wonder why this happens:
bbb = 5; // legal
int main(void) {
aaa = 10; // illegal
auto aaa = 10 // legal
Inside function a specifier is needed. Error message with no specifier used is:
error: ‘aaa’ undeclared (first use in this function)
Is this because of linkage - bbb variable has an external linkage so compiler knows that we are defining a variable here while inside mean() we need to show compiler that aaa is defined right here, it does not come from external functions?
Visual C++ :: Static Variables Local Or Global?
Mar 10, 2014I came across the following code today and I was a bit surprised that it worked:-
Code:
std::string func_A () {
static std::string x;
if (!x.empty())
return x;
[Code] ....
I've simplified things slightly - but the basic point is that both functions are in the same source file and they both have a static std::string called 'x'. Being static, I guess they aren't (strictly) local variables. So how does the compiler know that they're different entities? Does it encode their signatures using the function name or something like that? If I call each function separately I do seem to get the correct string...
C :: Compiling Sudoku Program - Declare Constant Instances As Global Variables
Sep 18, 2013I am trying to compile a c program for sudoku. I have declare const instances as global variables, but when i try to compile the code it says that my declarations are not constant, here is some of the code.
#include <stdio.h>
#include <assert.h>
const int GRIDSIZE = 3;
const int GRID_SQUARED = GRIDSIZE * GRIDSIZE; //this line
const int ALL_VALUES = (1<<GRID_SQUARED)-1; //and this give//the error
int board [GRID_SQUARED][GRID_SQUARED];
C/C++ :: Passing By Value With Two Variables
Jun 24, 2014This is my first time working with C++ and I have put together this program and came up with two errors and I am unsure what it is wanting me to do. The errors I got are:
1>c:usersownerdocumentsvisual studio 2010projectsweek5week5passing_by_value.cpp(30): error C2064: term does not evaluate to a function taking 1 arguments
1>c:usersownerdocumentsvisual studio 2010projectsweek5week5passing_by_value.cpp(38): error C2064: term does not evaluate to a function taking 1 arguments
#include<iostream>
using std::cin;
using std::cout;
using std::endl;
[Code].....
C :: Passing Variables Among Functions
Mar 6, 2015I have this code where I am trying to retrieve the contents of the variable dev1 and dev2. for some reason when i compile and run I am getting 0 and 0.
Code:
typedef struct {
uint32_t x;
uint32_t y;
} sample;
void get_sample(sample *one)
[Code].....
C++ :: Passing Variables Into A Function
Mar 29, 2014ok I have a class Player with lots of variables and im gonna call a function to checkXp, if I call it with the whole player object does it use a lot more memory then if I just passed the couple things I need?
ex
checkXP(Player* play) // this is a whole object of player
or
checkXP(play->getXP(), play->getLVL()) // the variables I want.
I just realized I may not be able to modify anything from player in the checkXP() function
question 1: does passing the whole object use more memory
question 2: if I passed as just the variables I need, I wont be able to modify anything of object play?
C++ :: Variables Not Passing Correctly
Mar 10, 2013Well I have my program running and the Variables are not passing correctly and the return statements are not returning correctly. Here is the parts that are not working.
#include <iostream>
#include "fight.h"
#include <time.h>
#include "player.h"
#include "stdlib.h"
#include <cstdlib>
using namespace std;
combat A;
combat::combat(void)
[Code] ....
C++ :: Passing Variables Between Functions
Jan 29, 2013I need passing some variables between functions. Here is the first part of the code which does work.
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
struct CarType {
string maker;
[Code] ....
Now the book says to take the following program and add a member function to the CarType class which prints the values of all of its data members. Add two more data members which are relevant for cars. Add the use of these data members to the program (to the assignment statements for MyCar, to the operator prompt and input inside the getYourCar function, and to the print function you have created).
Here is my code. Whenever I run it, it takes my assigned variables in MyCar and prints those instead of the one which the user is inputting.
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
using namespace std;
struct CarType {
string maker;
[Code] .....
C++ :: Passing Array Of Variables By Reference?
Sep 10, 2014I define an integer variable and pass it by reference to a function.
int func(int &x)
{
// do something
}
int x;
func(x);
However, I have not only one variable but an array of variables with its predefined name. How do I pass to the function by using loop? Example:
int x, y, z;
func(x);
func(y);
func(z);
How can I do this by using loop?
C :: Save Data From Global Variable Into Linked List
Jul 6, 2013I'm trying to run so called student-administration program.I got functions that can read and write student data, but the one saving the data from about 30 students has some problem that I can't figure. (warning: I'm quite new to C programming)so this is the code:..I guess I can't use global variables as function arguments?
Code:
//global variables
static char ReturnName[31];
static char ReturnFirstName[31];
static float ReturnAverage;
}
[code]....
incompatible types when assigning to type 'char[31]' from type 'int'
C++ :: Passing Both Private And Public Variables-functions?
Mar 6, 2015How to properly pass both private and public variables/functions from one class to another?
View 3 Replies View RelatedC :: Passing Int And Float Variables From Main And Getting Values From Another Function
Feb 3, 2015I have the main() - which has entries like
Code:
main() {
int ss, ret, z;
float yy;
ret = function1(&yy, &ss, &z);
//int function1(flat *cc, int *dd, int *k) - is it correct?
[Code]...
Visual C++ :: Passing DDX Control Variables Between Dialogs (Parent->Child)
Jul 19, 2013I have a main dialog which has (DDX?) controls for the user. eg a slider, and a combo box.
Previously, an image adjusted by these controls was in the same dialog.
I need to put this image in a New, separate dialog but it still must be controlled by the slider and combo box on the main dialog.
My question is how can I pass the control's variables between the dialogs? I have, say,
Code:
//MainDlg.cpp
DDX_Control(pDX, IDC_ComboBrightness, m_Brightness
I was told that I could do something like:
Code:
//ImageDlg.h
public:
ImageDlg(CWnd* pParent = NULL, CComboBox m_Brightness); // standard constructor
But I get errors including: Missing default parameter for parameter 2
I also need to pass the image array, is that perhaps the same method?
C++ :: Reading Variables From Data File
Feb 18, 2014I can't get my program to read the rest of my variables from my data file it will only read the first two and my end of file won't work it keeps continuing on.
879.46
C 400.00
D 100.0
F 525.00
C 450.00
D 500.00
D 1000.00
C 2000.00
D 3000.00
D 3500.00
C 5500.00
C 500.00
B 200.00
C -235.00
D 250.00
H -500.00
D 500.00
E
That's my data it will only read the inital number and C and D but nothing else.
// develop algorithm to balance checking account make transactions
#include<iostream> // required for keyboard and screen I/O
#include<fstream> // required for external file stream
#include<iomanip>
#include<conio.h>
#include<string>
[Code] ......
C :: Passing Data From An Array And Using It In Another
Mar 18, 2014I have been asked to write a lottery program in c using 5 separate functions 1 to take 6 numbers from user 2 to display the numbers 3 to sort the numbers 4 compare the chosen numbers to the winning numbers and 5 to list the frequency the user pick a number depending on how many times they play the game the problem im having is with the first 2 functions i can take the input and pass it to a display function but cannot get it to display the numbers here is what i have. The output from this is at the bottom .....
Code:
//function prototypes
int myNumbers();
void displayNums();
void sort();
void compare();
#include <stdio.h>
#define NUMS 6
#define WIN 7
[Code] .....
"Please enter your lucky numbers
1
2
3
4
5
6
Your numbers are 2286612"
C# :: DLL Passing And Retrieving Data
Sep 18, 2013I have a C# program going and want to be able to call the DLL and receive back the data requested through a pointer.Below is the DLL import within my C# code.
Code:
[DllImport("MyTest.dll")]
public static extern int ReadNetwork(Byte[] ROM_ID); Below is the code in the DLL Code: int _stdcall ReadNetwork(unsigned char* Array1)
{
ReadDevice(readBackArray);
for(i = 0; i < 20; i++)
{
Array1[i] = readBackArray[i];
}
[code]....
I've tried changing the return values in the DLL's ReadNetwork() function and that works ok, so I know I'm calling the DLL and it runs ok, but printing the result back is where I'm having the problem.
C++ :: Fastest Way Of Passing Data To A Class
Apr 25, 2013I'm currently building a new data structures that will be used in monte carlo generators (and so will be constructed several million times) and I'm wondering what's the best way (computer-speed-wise) to pass the data to the constructor. I am currently doing it using references and passing arrays as pointers like this:
Code:
class particle{
public:
particle(double *ar,int &id):IDup(id){
for (int i=0;i<5;++i)
Pup[i]=ar[i];
}
int IDup;
double Pup[5];
};
I'm assuming that since using references has no need to create a temporary memory slot it's more efficient .....
As for the arrays: is there a way for me to pass them as reference as well? (not using c++11), I'm using arrays instead of vectors as much as I can because I assume that vectors, being more advanced data structures, would take more time to create.
C :: Passing Arrays To Other Data Has Pointers?
May 7, 2013I am looking for an example of when passing arrays to other data that has pointers,
I understand the terms I would just like to see a small example of code that actually demonstrates this process.
C++ :: Passing Data Through A Void Function
Mar 11, 2013I am new to C++ ... My question is if I were to pass some data or values from the main() function through a void function (which main purpose is to display the data in a certain manner); how should one go about doing so?
For instance:
Code:
// example.cpp -- poorly written, just trying to learn
#include <iostream>
void format() {
using namespace std;
cout << "Time: " << min << hrs << endl;
[Code] .....
Obviously this is really poorly written, and confusing for the user. My main goal is to learn how to pass through values to a void function.
Also a bit off-topic, but is there a downside to place "using namespace std;" outside a function say if out of 100 functions only 10 of them use it? Would it make the program slower/unstable in any way or is this something one could do without any downsides?